An air guide device of the general type in question is known from, for example, EP 0 226 778 A2, which comprises an air guide element and a plate-shaped closure part, designed as an underflow guard. The closure part is designed as an integral part of the air guide element and is thus adjusted together with the guide element between a rest position and an operating position.
Another air guide device, which is arranged in a rear area of a motor vehicle, is known from DE 44 27 196 A1. This device can be moved by an adjusting device from a retracted rest position into an extended operating position. To create a highly effective air guide device which takes up a minimum of space in its rest position, it is provided that the air guide device can be retracted and extended in the height direction of the vehicle and that, when in the operating position, it is connected over its entire transverse dimension to the underlying structure in a manner which prevents the passage of air and also projects above this structure.
Finally, an air guide device for guiding the air flow along a motor vehicle is known from DE 10 2004 043 544 A1. To prevent the air from flowing underneath a spoiler blade and at the same time to be able to carry away intruding water effectively, an underflow guard, which prevents air from flowing underneath the spoiler blade, and a water guide device, which carries away the water coming from the spoiler blade or present in its environment, are provided as integral parts of the spoiler blade.